A continuation of studies on the biosynthesis of fatty acids, cholesterol and carotenes is proposed. The emphasis in these studies will, however, be placed on the biosynthesis of fatty acids. Attempts will be made to develop a new method of separation of the nonidentical half-molecular weight subunits of pigeon and rat liver fatty acid synthetases. These methods will utilize immunochemical techniques and affinity chromatography. Antisera to each subunit will then be prepared. A reinvestigation of the properties of each subunit will then be carried out. Attempts will then be made to establish some of the structural organization of the fatty acid synthetase subunits via treatment with specific proteases. Studies will also continue on the purification, properties and regulation of the enzymes that bring about the interconversion of apo- and holofatty acid synthetase. Investigations on the isolation, purification and translation of mRNA for the fatty acid synthetase complex will also continue. Determination will be made, too, of the variation in content of the mRNA in livers of animals subjected to different nutritional or hormonal states. Studies on acetyl-CoA carboxylase will be concentrated largely on the isolation, purification and identification of a factor that regulates the activity of this enzyme. Investigations on the effect of glucagon on the regulatory factor will also be carried out. Studies on the biosynthesis of cholesterol will be concerned mainly with the preparation of a monospecific antibody to HMG-CoA reductase. When this task is achieved, attempts will be made to isolate the mRNA for HMG-CoA reductase and to determine the variation in content of this mRNA with nutritional and hormonal state of an animal. Studies on carotene biosynthesis will be concerned largely with the isolation and purification of enzymes that convert isopentenyl pyrophosphate to acyclic and cyclic carotenes.